Propeller



Nov. 19,1946. A. G. ALlzlER 2,411,143

PROPELLER Ill v Patented Nov. 19, 1946 PROPELLER Andr Georges Alizier,Chicago, Ill., assignor to Cornet Model Airplane & Supply Company,Incorporated, a corporation of Illinois Application November 15, 1943,Serial No. 510,329

4 Claims.

This invention relates to a propeller, and more particularly to apropeller for model airplanes.

One feature of this invention is that it provides an improved propellerfor a model airplane; another feature of this invention is that a veryeilicient and well balanced propeller may be constructed quickly andeihciently by the model builder; still another feature of this inventionis that both dynamic and static balancing of the propeller arepractically assured; and yet another feature of this invention is thatvtwo, three or four bladed propellers can be constructed with equal easeand with equally desirable results. Other features and advantages ofthis invention will be apparent from the following speciication and thedrawing, in which:

, Figure l is aperspective View of a iinished three-bladed propellerembodying this invention; Figure 2 is a partially exploded view of thesame propeller; Figure 3 is a fragmentary View of the propeller duringassembly, before bringing one of the hub members into place; Figure 4 isan enlarged sectional view of the propeller hub along a diameter thereof(as the line `ll-ll of Figure 3, with the blades removed) and Figure 5is a View of the propeller strip element in initial plane p0- sition.

The construction of model airplanes is receiving increasingly greaterattention, both for purposes of instruction and relaxation. Theconstruction and assembly of the fuselage and wings of a model airplane,by modern methods, is a pleasant and relatively short task; buthandshaping of a good propeller, by the methods heretoforeconventionally in use, has been dilcult and tedious. Heretofore, it hasbeen common to start with a rectangular block of Wood, or a very roughlyshaped piece of wood, and carve and sand the propeller into final shape.Securing good balance and proper symmetry of blade shapes was almost animpossibility by this method, one blade almost always carryingconsiderably more of the torque than the other, and a dynamicallyunbalanced propeller resulted. Moreover, this method of construction, asa practical proposition, resulted in the model airplane constructerbeing limited to two blade propellers whereas models of many modernplanes should be equipped with three or four bladed propellers.

I have devised and am here disclosing and claiming an improved methodfor simply making well balanced and eilicient propellers for modelairplanes, it being quite easy to make three and four bladed propellersin the manner here disclosed. Rather than attempting to get the complexcurvature necessary for constant pitch and approved airfoil shapes, Iuse thin, flat propeller blades, which may be die cut from thin sheet`material, as heavy cardboard or Very light wood or hand cut orpre-shaped along lines printed on the sheet material. I- form the hubcarrying these blades by spaced parallel front and back members with aperipheral strip element, this strip element having slots at the sameangle and symmetrically arranged around the hub. The blades are slippedinto the slots, properly centered, and then fastened in place .bycementi-ng or other appropriate means.

Referring now more particularly to the specic embodiment of this`invention illustrated.

herewith, it will be seen that the hub-comprises two flat polygonalmembers Il) and II (he-reshown as hexagonal) `adapted to be held inspaced parallel relationship by a peripheral strip element I2, shown inits initial or flat form in Figure V5. The members Il) and II arepreferablyl of the same size and of sheet material such as light wood orheavy cardboard.

Referring now more particularly to Figure 5, it will be seen that thestrip vI 2 is provided with three slots here identified as IZa, IIZb andI2C. These are at an appropriate acute angle to the edges of the strip(and thus at this same angle to the front and back members Il) and -IIwhen the hub is assembled) as, for example, 35; and they are so spacedthat, when the hub is assembled, they will be symmetrically arranged orequally spaced about the periphery of the hub. The ends of the stripelement are, of course, cemented to each other; and both edges of theelement are cemented to the respective front and back members I il andII, so called because they `face to the front and to the back of theairplane when the propeller is in operative position thereon. The word"cemented is used here in a broad sense, being intended to includegluing, lacquer, or any adhesive for binding the parts together.

The three blades, here identified as I3, I4 and I5, are identical witheach other, being die stamped or pre-shaped in accordance with adelinite pattern from light sheet material, as thin wood or fairly heavycardboard. The blades are preferably rounded at the tip, somewhatenlarged toward the outer end, and reduced at the end adapted to beassociated with the propeller, hereinafter termed the inner end, asshown. This shaping results in the outer half of each propeller bladedeveloping more than three-quarters of the total possible power, so thatthere is no appreciable loss in eiciency due to the use of a 3 flatblade, as contrasted with a, constant pitch blade having a greater anglenear the hub. As may be best seen in Figures 2 and 3, the inner ends ofthe blades are provided with identical l-shaped notches, as the notchl3a of the blade In assembling the propeller, the members I and Il areproperly related to each other (as by passing a pin I6 through centralopenings in these members), and the strip element I2 is Wrapped aroundthe periphery of these members,

the ends of the strip element then being cemented to each other, and oneedge of the strip element being cemented to one of the members, as themember Il. The reduced ends of the blades I3, i4 and l5 are then slippedinto the slots l2a-c and the V-shaped slots interlocked with each otheraround the pin to ensure proper centering and alignment of the blades.Two of the blades are shown in position in Figure 2 and the third bladein Figure 3. When the parts have been thus assembled, the inner ends ofthe blade are cemented to each other and the parts passing through theslots are cemented to the strip at that point. After this is vdone theother member l0 is cemented in place and the pin I6 removed, the nishedpropeller then being as shown in Figure 1.

It will be readily apparent thata light, sturdy, symmetrical and wellbalanced propeller can be readily made in this manner with any desirednumber of blades. It has proved somewhat more desirable, for properinter-relation between the slot and the part of the blade passingthrough it, to use polygonal end members with double the number of sidesthat therey are blades, so that a at side is provided for each blade.That is, hexagonal members may be used for a three blade propeller,octagonal members for a four blade propeller, etc.

While I have shown and `described certain embodiments of my invention,it is to be understood that it is capable of many modifications.Changes, therefore, in the construction and arrangement may be madewithout departing from the spirit and scope of the invention asdisclosed in the appended claims.

I claim:

1. A light-Weight propeller for a model air- 4 plane, including: a hubcomprising spaced, parallel, similarly polygonal, front and back membershaving an even number of sides, said sides being at least six in number,a, peripheral element holding the members in said spaced relationship,slots symmetrically arranged in said peripheral lelement between thefront and back members with all slots making substantially the sameangle withsaid members, said slots being equal in number to one-half thenumber of polygonal sides in one of said members and each slot beingcentered between corresponding sides of said polygonal members; and ailat, planar propeller blade for each slot having a reduced end held bysaid slot.

2. A method of constructing a propeller for model airplanes, comprisingshaping at blades from plane sheet material, shaping front and back hubmembers from plane sheet material, forming a slotted strip of sheetmaterial around the periphery of one of said members, inserting a smallrod-like element through the center of the hub members for centering theinner ends of said blades, inserting the blades in the slots in saidstrip, removing the rod-like element, iastening the blades together andto the strip, andv bringing the other hub member into place.

3. A light Weight propeller for a model airplane, including: a pluralityof flat, pre-shaped blades having one end of each reduced in size; and ahub comprising spaced, parallel front and back members and a slottedperipheral element of sheet material, said slots being symmetricallyarranged around the hub and all making the same angle with said members,said slots re,- ceiving the reduced ends of said blade, said ends ofsaid blades interlocking with each other atl the center of said hub.

4. A light weight propeller for a model airl

